xref: /linux/net/smc/smc_llc.c (revision 56e8091c7a098ef2257f85f16665d79cf3049da9)

// SPDX-License-Identifier: GPL-2.0
/*
 *  Shared Memory Communications over RDMA (SMC-R) and RoCE
 *
 *  Link Layer Control (LLC)
 *
 *  Copyright IBM Corp. 2016
 *
 *  Author(s):  Klaus Wacker <Klaus.Wacker@de.ibm.com>
 *              Ursula Braun <ubraun@linux.vnet.ibm.com>
 */

#include <net/tcp.h>
#include <rdma/ib_verbs.h>

#include "smc.h"
#include "smc_core.h"
#include "smc_clc.h"
#include "smc_llc.h"

#define SMC_LLC_DATA_LEN		40

struct smc_llc_hdr {
	struct smc_wr_rx_hdr common;
	u8 length;	/* 44 */
#if defined(__BIG_ENDIAN_BITFIELD)
	u8 reserved:4,
	   add_link_rej_rsn:4;
#elif defined(__LITTLE_ENDIAN_BITFIELD)
	u8 add_link_rej_rsn:4,
	   reserved:4;
#endif
	u8 flags;
};

#define SMC_LLC_FLAG_NO_RMBE_EYEC	0x03

struct smc_llc_msg_confirm_link {	/* type 0x01 */
	struct smc_llc_hdr hd;
	u8 sender_mac[ETH_ALEN];
	u8 sender_gid[SMC_GID_SIZE];
	u8 sender_qp_num[3];
	u8 link_num;
	u8 link_uid[SMC_LGR_ID_SIZE];
	u8 max_links;
	u8 reserved[9];
};

#define SMC_LLC_FLAG_ADD_LNK_REJ	0x40
#define SMC_LLC_REJ_RSN_NO_ALT_PATH	1

#define SMC_LLC_ADD_LNK_MAX_LINKS	2

struct smc_llc_msg_add_link {		/* type 0x02 */
	struct smc_llc_hdr hd;
	u8 sender_mac[ETH_ALEN];
	u8 reserved2[2];
	u8 sender_gid[SMC_GID_SIZE];
	u8 sender_qp_num[3];
	u8 link_num;
	u8 flags2;	/* QP mtu */
	u8 initial_psn[3];
	u8 reserved[8];
};

#define SMC_LLC_FLAG_DEL_LINK_ALL	0x40
#define SMC_LLC_FLAG_DEL_LINK_ORDERLY	0x20

struct smc_llc_msg_del_link {		/* type 0x04 */
	struct smc_llc_hdr hd;
	u8 link_num;
	__be32 reason;
	u8 reserved[35];
} __packed;			/* format defined in RFC7609 */

struct smc_llc_msg_test_link {		/* type 0x07 */
	struct smc_llc_hdr hd;
	u8 user_data[16];
	u8 reserved[24];
};

struct smc_rmb_rtoken {
	union {
		u8 num_rkeys;	/* first rtoken byte of CONFIRM LINK msg */
				/* is actually the num of rtokens, first */
				/* rtoken is always for the current link */
		u8 link_id;	/* link id of the rtoken */
	};
	__be32 rmb_key;
	__be64 rmb_vaddr;
} __packed;			/* format defined in RFC7609 */

#define SMC_LLC_RKEYS_PER_MSG	3

struct smc_llc_msg_confirm_rkey {	/* type 0x06 */
	struct smc_llc_hdr hd;
	struct smc_rmb_rtoken rtoken[SMC_LLC_RKEYS_PER_MSG];
	u8 reserved;
};

struct smc_llc_msg_confirm_rkey_cont {	/* type 0x08 */
	struct smc_llc_hdr hd;
	u8 num_rkeys;
	struct smc_rmb_rtoken rtoken[SMC_LLC_RKEYS_PER_MSG];
};

#define SMC_LLC_DEL_RKEY_MAX	8
#define SMC_LLC_FLAG_RKEY_NEG	0x20

struct smc_llc_msg_delete_rkey {	/* type 0x09 */
	struct smc_llc_hdr hd;
	u8 num_rkeys;
	u8 err_mask;
	u8 reserved[2];
	__be32 rkey[8];
	u8 reserved2[4];
};

union smc_llc_msg {
	struct smc_llc_msg_confirm_link confirm_link;
	struct smc_llc_msg_add_link add_link;
	struct smc_llc_msg_del_link delete_link;

	struct smc_llc_msg_confirm_rkey confirm_rkey;
	struct smc_llc_msg_confirm_rkey_cont confirm_rkey_cont;
	struct smc_llc_msg_delete_rkey delete_rkey;

	struct smc_llc_msg_test_link test_link;
	struct {
		struct smc_llc_hdr hdr;
		u8 data[SMC_LLC_DATA_LEN];
	} raw;
};

#define SMC_LLC_FLAG_RESP		0x80

struct smc_llc_qentry {
	struct list_head list;
	struct smc_link *link;
	union smc_llc_msg msg;
};

struct smc_llc_qentry *smc_llc_flow_qentry_clr(struct smc_llc_flow *flow)
{
	struct smc_llc_qentry *qentry = flow->qentry;

	flow->qentry = NULL;
	return qentry;
}

void smc_llc_flow_qentry_del(struct smc_llc_flow *flow)
{
	struct smc_llc_qentry *qentry;

	if (flow->qentry) {
		qentry = flow->qentry;
		flow->qentry = NULL;
		kfree(qentry);
	}
}

static inline void smc_llc_flow_qentry_set(struct smc_llc_flow *flow,
					   struct smc_llc_qentry *qentry)
{
	flow->qentry = qentry;
}

/* try to start a new llc flow, initiated by an incoming llc msg */
static bool smc_llc_flow_start(struct smc_llc_flow *flow,
			       struct smc_llc_qentry *qentry)
{
	struct smc_link_group *lgr = qentry->link->lgr;

	spin_lock_bh(&lgr->llc_flow_lock);
	if (flow->type) {
		/* a flow is already active */
		if ((qentry->msg.raw.hdr.common.type == SMC_LLC_ADD_LINK ||
		     qentry->msg.raw.hdr.common.type == SMC_LLC_DELETE_LINK) &&
		    !lgr->delayed_event) {
			lgr->delayed_event = qentry;
		} else {
			/* forget this llc request */
			kfree(qentry);
		}
		spin_unlock_bh(&lgr->llc_flow_lock);
		return false;
	}
	switch (qentry->msg.raw.hdr.common.type) {
	case SMC_LLC_ADD_LINK:
		flow->type = SMC_LLC_FLOW_ADD_LINK;
		break;
	case SMC_LLC_DELETE_LINK:
		flow->type = SMC_LLC_FLOW_DEL_LINK;
		break;
	case SMC_LLC_CONFIRM_RKEY:
	case SMC_LLC_DELETE_RKEY:
		flow->type = SMC_LLC_FLOW_RKEY;
		break;
	default:
		flow->type = SMC_LLC_FLOW_NONE;
	}
	if (qentry == lgr->delayed_event)
		lgr->delayed_event = NULL;
	spin_unlock_bh(&lgr->llc_flow_lock);
	smc_llc_flow_qentry_set(flow, qentry);
	return true;
}

/* start a new local llc flow, wait till current flow finished */
int smc_llc_flow_initiate(struct smc_link_group *lgr,
			  enum smc_llc_flowtype type)
{
	enum smc_llc_flowtype allowed_remote = SMC_LLC_FLOW_NONE;
	int rc;

	/* all flows except confirm_rkey and delete_rkey are exclusive,
	 * confirm/delete rkey flows can run concurrently (local and remote)
	 */
	if (type == SMC_LLC_FLOW_RKEY)
		allowed_remote = SMC_LLC_FLOW_RKEY;
again:
	if (list_empty(&lgr->list))
		return -ENODEV;
	spin_lock_bh(&lgr->llc_flow_lock);
	if (lgr->llc_flow_lcl.type == SMC_LLC_FLOW_NONE &&
	    (lgr->llc_flow_rmt.type == SMC_LLC_FLOW_NONE ||
	     lgr->llc_flow_rmt.type == allowed_remote)) {
		lgr->llc_flow_lcl.type = type;
		spin_unlock_bh(&lgr->llc_flow_lock);
		return 0;
	}
	spin_unlock_bh(&lgr->llc_flow_lock);
	rc = wait_event_interruptible_timeout(lgr->llc_waiter,
			(lgr->llc_flow_lcl.type == SMC_LLC_FLOW_NONE &&
			 (lgr->llc_flow_rmt.type == SMC_LLC_FLOW_NONE ||
			  lgr->llc_flow_rmt.type == allowed_remote)),
			SMC_LLC_WAIT_TIME);
	if (!rc)
		return -ETIMEDOUT;
	goto again;
}

/* finish the current llc flow */
void smc_llc_flow_stop(struct smc_link_group *lgr, struct smc_llc_flow *flow)
{
	spin_lock_bh(&lgr->llc_flow_lock);
	memset(flow, 0, sizeof(*flow));
	flow->type = SMC_LLC_FLOW_NONE;
	spin_unlock_bh(&lgr->llc_flow_lock);
	if (!list_empty(&lgr->list) && lgr->delayed_event &&
	    flow == &lgr->llc_flow_lcl)
		schedule_work(&lgr->llc_event_work);
	else
		wake_up_interruptible(&lgr->llc_waiter);
}

/* lnk is optional and used for early wakeup when link goes down, useful in
 * cases where we wait for a response on the link after we sent a request
 */
struct smc_llc_qentry *smc_llc_wait(struct smc_link_group *lgr,
				    struct smc_link *lnk,
				    int time_out, u8 exp_msg)
{
	struct smc_llc_flow *flow = &lgr->llc_flow_lcl;

	wait_event_interruptible_timeout(lgr->llc_waiter,
					 (flow->qentry ||
					  (lnk && !smc_link_usable(lnk)) ||
					  list_empty(&lgr->list)),
					 time_out);
	if (!flow->qentry ||
	    (lnk && !smc_link_usable(lnk)) || list_empty(&lgr->list)) {
		smc_llc_flow_qentry_del(flow);
		goto out;
	}
	if (exp_msg && flow->qentry->msg.raw.hdr.common.type != exp_msg) {
		if (exp_msg == SMC_LLC_ADD_LINK &&
		    flow->qentry->msg.raw.hdr.common.type ==
		    SMC_LLC_DELETE_LINK) {
			/* flow_start will delay the unexpected msg */
			smc_llc_flow_start(&lgr->llc_flow_lcl,
					   smc_llc_flow_qentry_clr(flow));
			return NULL;
		}
		smc_llc_flow_qentry_del(flow);
	}
out:
	return flow->qentry;
}

/********************************** send *************************************/

struct smc_llc_tx_pend {
};

/* handler for send/transmission completion of an LLC msg */
static void smc_llc_tx_handler(struct smc_wr_tx_pend_priv *pend,
			       struct smc_link *link,
			       enum ib_wc_status wc_status)
{
	/* future work: handle wc_status error for recovery and failover */
}

/**
 * smc_llc_add_pending_send() - add LLC control message to pending WQE transmits
 * @link: Pointer to SMC link used for sending LLC control message.
 * @wr_buf: Out variable returning pointer to work request payload buffer.
 * @pend: Out variable returning pointer to private pending WR tracking.
 *	  It's the context the transmit complete handler will get.
 *
 * Reserves and pre-fills an entry for a pending work request send/tx.
 * Used by mid-level smc_llc_send_msg() to prepare for later actual send/tx.
 * Can sleep due to smc_get_ctrl_buf (if not in softirq context).
 *
 * Return: 0 on success, otherwise an error value.
 */
static int smc_llc_add_pending_send(struct smc_link *link,
				    struct smc_wr_buf **wr_buf,
				    struct smc_wr_tx_pend_priv **pend)
{
	int rc;

	rc = smc_wr_tx_get_free_slot(link, smc_llc_tx_handler, wr_buf, NULL,
				     pend);
	if (rc < 0)
		return rc;
	BUILD_BUG_ON_MSG(
		sizeof(union smc_llc_msg) > SMC_WR_BUF_SIZE,
		"must increase SMC_WR_BUF_SIZE to at least sizeof(struct smc_llc_msg)");
	BUILD_BUG_ON_MSG(
		sizeof(union smc_llc_msg) != SMC_WR_TX_SIZE,
		"must adapt SMC_WR_TX_SIZE to sizeof(struct smc_llc_msg); if not all smc_wr upper layer protocols use the same message size any more, must start to set link->wr_tx_sges[i].length on each individual smc_wr_tx_send()");
	BUILD_BUG_ON_MSG(
		sizeof(struct smc_llc_tx_pend) > SMC_WR_TX_PEND_PRIV_SIZE,
		"must increase SMC_WR_TX_PEND_PRIV_SIZE to at least sizeof(struct smc_llc_tx_pend)");
	return 0;
}

/* high-level API to send LLC confirm link */
int smc_llc_send_confirm_link(struct smc_link *link,
			      enum smc_llc_reqresp reqresp)
{
	struct smc_link_group *lgr = smc_get_lgr(link);
	struct smc_llc_msg_confirm_link *confllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	confllc = (struct smc_llc_msg_confirm_link *)wr_buf;
	memset(confllc, 0, sizeof(*confllc));
	confllc->hd.common.type = SMC_LLC_CONFIRM_LINK;
	confllc->hd.length = sizeof(struct smc_llc_msg_confirm_link);
	confllc->hd.flags |= SMC_LLC_FLAG_NO_RMBE_EYEC;
	if (reqresp == SMC_LLC_RESP)
		confllc->hd.flags |= SMC_LLC_FLAG_RESP;
	memcpy(confllc->sender_mac, link->smcibdev->mac[link->ibport - 1],
	       ETH_ALEN);
	memcpy(confllc->sender_gid, link->gid, SMC_GID_SIZE);
	hton24(confllc->sender_qp_num, link->roce_qp->qp_num);
	confllc->link_num = link->link_id;
	memcpy(confllc->link_uid, lgr->id, SMC_LGR_ID_SIZE);
	confllc->max_links = SMC_LLC_ADD_LNK_MAX_LINKS; /* enforce peer resp. */
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* send LLC confirm rkey request */
static int smc_llc_send_confirm_rkey(struct smc_link *send_link,
				     struct smc_buf_desc *rmb_desc)
{
	struct smc_llc_msg_confirm_rkey *rkeyllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	struct smc_link *link;
	int i, rc, rtok_ix;

	rc = smc_llc_add_pending_send(send_link, &wr_buf, &pend);
	if (rc)
		return rc;
	rkeyllc = (struct smc_llc_msg_confirm_rkey *)wr_buf;
	memset(rkeyllc, 0, sizeof(*rkeyllc));
	rkeyllc->hd.common.type = SMC_LLC_CONFIRM_RKEY;
	rkeyllc->hd.length = sizeof(struct smc_llc_msg_confirm_rkey);

	rtok_ix = 1;
	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
		link = &send_link->lgr->lnk[i];
		if (link->state == SMC_LNK_ACTIVE && link != send_link) {
			rkeyllc->rtoken[rtok_ix].link_id = link->link_id;
			rkeyllc->rtoken[rtok_ix].rmb_key =
				htonl(rmb_desc->mr_rx[link->link_idx]->rkey);
			rkeyllc->rtoken[rtok_ix].rmb_vaddr = cpu_to_be64(
				(u64)sg_dma_address(
					rmb_desc->sgt[link->link_idx].sgl));
			rtok_ix++;
		}
	}
	/* rkey of send_link is in rtoken[0] */
	rkeyllc->rtoken[0].num_rkeys = rtok_ix - 1;
	rkeyllc->rtoken[0].rmb_key =
		htonl(rmb_desc->mr_rx[send_link->link_idx]->rkey);
	rkeyllc->rtoken[0].rmb_vaddr = cpu_to_be64(
		(u64)sg_dma_address(rmb_desc->sgt[send_link->link_idx].sgl));
	/* send llc message */
	rc = smc_wr_tx_send(send_link, pend);
	return rc;
}

/* send LLC delete rkey request */
static int smc_llc_send_delete_rkey(struct smc_link *link,
				    struct smc_buf_desc *rmb_desc)
{
	struct smc_llc_msg_delete_rkey *rkeyllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	rkeyllc = (struct smc_llc_msg_delete_rkey *)wr_buf;
	memset(rkeyllc, 0, sizeof(*rkeyllc));
	rkeyllc->hd.common.type = SMC_LLC_DELETE_RKEY;
	rkeyllc->hd.length = sizeof(struct smc_llc_msg_delete_rkey);
	rkeyllc->num_rkeys = 1;
	rkeyllc->rkey[0] = htonl(rmb_desc->mr_rx[link->link_idx]->rkey);
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* prepare an add link message */
static void smc_llc_prep_add_link(struct smc_llc_msg_add_link *addllc,
				  struct smc_link *link, u8 mac[], u8 gid[],
				  enum smc_llc_reqresp reqresp)
{
	memset(addllc, 0, sizeof(*addllc));
	addllc->hd.common.type = SMC_LLC_ADD_LINK;
	addllc->hd.length = sizeof(struct smc_llc_msg_add_link);
	if (reqresp == SMC_LLC_RESP) {
		addllc->hd.flags |= SMC_LLC_FLAG_RESP;
		/* always reject more links for now */
		addllc->hd.flags |= SMC_LLC_FLAG_ADD_LNK_REJ;
		addllc->hd.add_link_rej_rsn = SMC_LLC_REJ_RSN_NO_ALT_PATH;
	}
	memcpy(addllc->sender_mac, mac, ETH_ALEN);
	memcpy(addllc->sender_gid, gid, SMC_GID_SIZE);
}

/* send ADD LINK request or response */
int smc_llc_send_add_link(struct smc_link *link, u8 mac[], u8 gid[],
			  enum smc_llc_reqresp reqresp)
{
	struct smc_llc_msg_add_link *addllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	addllc = (struct smc_llc_msg_add_link *)wr_buf;
	smc_llc_prep_add_link(addllc, link, mac, gid, reqresp);
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* prepare a delete link message */
static void smc_llc_prep_delete_link(struct smc_llc_msg_del_link *delllc,
				     struct smc_link *link,
				     enum smc_llc_reqresp reqresp, bool orderly)
{
	memset(delllc, 0, sizeof(*delllc));
	delllc->hd.common.type = SMC_LLC_DELETE_LINK;
	delllc->hd.length = sizeof(struct smc_llc_msg_add_link);
	if (reqresp == SMC_LLC_RESP)
		delllc->hd.flags |= SMC_LLC_FLAG_RESP;
	/* DEL_LINK_ALL because only 1 link supported */
	delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ALL;
	if (orderly)
		delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ORDERLY;
	delllc->link_num = link->link_id;
}

/* send DELETE LINK request or response */
int smc_llc_send_delete_link(struct smc_link *link,
			     enum smc_llc_reqresp reqresp, bool orderly)
{
	struct smc_llc_msg_del_link *delllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	delllc = (struct smc_llc_msg_del_link *)wr_buf;
	smc_llc_prep_delete_link(delllc, link, reqresp, orderly);
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* send LLC test link request */
static int smc_llc_send_test_link(struct smc_link *link, u8 user_data[16])
{
	struct smc_llc_msg_test_link *testllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	testllc = (struct smc_llc_msg_test_link *)wr_buf;
	memset(testllc, 0, sizeof(*testllc));
	testllc->hd.common.type = SMC_LLC_TEST_LINK;
	testllc->hd.length = sizeof(struct smc_llc_msg_test_link);
	memcpy(testllc->user_data, user_data, sizeof(testllc->user_data));
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* schedule an llc send on link, may wait for buffers */
static int smc_llc_send_message(struct smc_link *link, void *llcbuf)
{
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	if (!smc_link_usable(link))
		return -ENOLINK;
	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	memcpy(wr_buf, llcbuf, sizeof(union smc_llc_msg));
	return smc_wr_tx_send(link, pend);
}

/********************************* receive ***********************************/

static void smc_llc_rx_delete_link(struct smc_link *link,
				   struct smc_llc_msg_del_link *llc)
{
	struct smc_link_group *lgr = smc_get_lgr(link);

	smc_lgr_forget(lgr);
	smc_llc_link_deleting(link);
	if (lgr->role == SMC_SERV) {
		/* client asks to delete this link, send request */
		smc_llc_prep_delete_link(llc, link, SMC_LLC_REQ, true);
	} else {
		/* server requests to delete this link, send response */
		smc_llc_prep_delete_link(llc, link, SMC_LLC_RESP, true);
	}
	smc_llc_send_message(link, llc);
	smc_lgr_terminate_sched(lgr);
}

static void smc_llc_rx_confirm_rkey(struct smc_link *link,
				    struct smc_llc_msg_confirm_rkey *llc)
{
	int rc;

	rc = smc_rtoken_add(link,
			    llc->rtoken[0].rmb_vaddr,
			    llc->rtoken[0].rmb_key);

	/* ignore rtokens for other links, we have only one link */

	llc->hd.flags |= SMC_LLC_FLAG_RESP;
	if (rc < 0)
		llc->hd.flags |= SMC_LLC_FLAG_RKEY_NEG;
	smc_llc_send_message(link, llc);
}

static void smc_llc_rx_confirm_rkey_cont(struct smc_link *link,
				      struct smc_llc_msg_confirm_rkey_cont *llc)
{
	/* ignore rtokens for other links, we have only one link */
	llc->hd.flags |= SMC_LLC_FLAG_RESP;
	smc_llc_send_message(link, llc);
}

static void smc_llc_rx_delete_rkey(struct smc_link *link,
				   struct smc_llc_msg_delete_rkey *llc)
{
	u8 err_mask = 0;
	int i, max;

	max = min_t(u8, llc->num_rkeys, SMC_LLC_DEL_RKEY_MAX);
	for (i = 0; i < max; i++) {
		if (smc_rtoken_delete(link, llc->rkey[i]))
			err_mask |= 1 << (SMC_LLC_DEL_RKEY_MAX - 1 - i);
	}

	if (err_mask) {
		llc->hd.flags |= SMC_LLC_FLAG_RKEY_NEG;
		llc->err_mask = err_mask;
	}

	llc->hd.flags |= SMC_LLC_FLAG_RESP;
	smc_llc_send_message(link, llc);
}

/* flush the llc event queue */
static void smc_llc_event_flush(struct smc_link_group *lgr)
{
	struct smc_llc_qentry *qentry, *q;

	spin_lock_bh(&lgr->llc_event_q_lock);
	list_for_each_entry_safe(qentry, q, &lgr->llc_event_q, list) {
		list_del_init(&qentry->list);
		kfree(qentry);
	}
	spin_unlock_bh(&lgr->llc_event_q_lock);
}

static void smc_llc_event_handler(struct smc_llc_qentry *qentry)
{
	union smc_llc_msg *llc = &qentry->msg;
	struct smc_link *link = qentry->link;
	struct smc_link_group *lgr = link->lgr;

	if (!smc_link_usable(link))
		goto out;

	switch (llc->raw.hdr.common.type) {
	case SMC_LLC_TEST_LINK:
		llc->test_link.hd.flags |= SMC_LLC_FLAG_RESP;
		smc_llc_send_message(link, llc);
		break;
	case SMC_LLC_ADD_LINK:
		if (list_empty(&lgr->list))
			goto out;	/* lgr is terminating */
		if (lgr->role == SMC_CLNT) {
			if (lgr->llc_flow_lcl.type == SMC_LLC_FLOW_ADD_LINK) {
				/* a flow is waiting for this message */
				smc_llc_flow_qentry_set(&lgr->llc_flow_lcl,
							qentry);
				wake_up_interruptible(&lgr->llc_waiter);
			} else if (smc_llc_flow_start(&lgr->llc_flow_lcl,
						      qentry)) {
				/* tbd: schedule_work(&lgr->llc_add_link_work); */
			}
		} else if (smc_llc_flow_start(&lgr->llc_flow_lcl, qentry)) {
			/* as smc server, handle client suggestion */
			/* tbd: schedule_work(&lgr->llc_add_link_work); */
		}
		return;
	case SMC_LLC_CONFIRM_LINK:
		if (lgr->llc_flow_lcl.type != SMC_LLC_FLOW_NONE) {
			/* a flow is waiting for this message */
			smc_llc_flow_qentry_set(&lgr->llc_flow_lcl, qentry);
			wake_up_interruptible(&lgr->llc_waiter);
			return;
		}
		break;
	case SMC_LLC_DELETE_LINK:
		smc_llc_rx_delete_link(link, &llc->delete_link);
		break;
	case SMC_LLC_CONFIRM_RKEY:
		smc_llc_rx_confirm_rkey(link, &llc->confirm_rkey);
		break;
	case SMC_LLC_CONFIRM_RKEY_CONT:
		smc_llc_rx_confirm_rkey_cont(link, &llc->confirm_rkey_cont);
		break;
	case SMC_LLC_DELETE_RKEY:
		smc_llc_rx_delete_rkey(link, &llc->delete_rkey);
		break;
	}
out:
	kfree(qentry);
}

/* worker to process llc messages on the event queue */
static void smc_llc_event_work(struct work_struct *work)
{
	struct smc_link_group *lgr = container_of(work, struct smc_link_group,
						  llc_event_work);
	struct smc_llc_qentry *qentry;

	if (!lgr->llc_flow_lcl.type && lgr->delayed_event) {
		if (smc_link_usable(lgr->delayed_event->link)) {
			smc_llc_event_handler(lgr->delayed_event);
		} else {
			qentry = lgr->delayed_event;
			lgr->delayed_event = NULL;
			kfree(qentry);
		}
	}

again:
	spin_lock_bh(&lgr->llc_event_q_lock);
	if (!list_empty(&lgr->llc_event_q)) {
		qentry = list_first_entry(&lgr->llc_event_q,
					  struct smc_llc_qentry, list);
		list_del_init(&qentry->list);
		spin_unlock_bh(&lgr->llc_event_q_lock);
		smc_llc_event_handler(qentry);
		goto again;
	}
	spin_unlock_bh(&lgr->llc_event_q_lock);
}

/* process llc responses in tasklet context */
static void smc_llc_rx_response(struct smc_link *link,
				struct smc_llc_qentry *qentry)
{
	u8 llc_type = qentry->msg.raw.hdr.common.type;

	switch (llc_type) {
	case SMC_LLC_TEST_LINK:
		if (link->state == SMC_LNK_ACTIVE)
			complete(&link->llc_testlink_resp);
		break;
	case SMC_LLC_ADD_LINK:
	case SMC_LLC_CONFIRM_LINK:
	case SMC_LLC_CONFIRM_RKEY:
	case SMC_LLC_DELETE_RKEY:
		/* assign responses to the local flow, we requested them */
		smc_llc_flow_qentry_set(&link->lgr->llc_flow_lcl, qentry);
		wake_up_interruptible(&link->lgr->llc_waiter);
		return;
	case SMC_LLC_DELETE_LINK:
		if (link->lgr->role == SMC_SERV)
			smc_lgr_schedule_free_work_fast(link->lgr);
		break;
	case SMC_LLC_CONFIRM_RKEY_CONT:
		/* unused as long as we don't send this type of msg */
		break;
	}
	kfree(qentry);
}

static void smc_llc_enqueue(struct smc_link *link, union smc_llc_msg *llc)
{
	struct smc_link_group *lgr = link->lgr;
	struct smc_llc_qentry *qentry;
	unsigned long flags;

	qentry = kmalloc(sizeof(*qentry), GFP_ATOMIC);
	if (!qentry)
		return;
	qentry->link = link;
	INIT_LIST_HEAD(&qentry->list);
	memcpy(&qentry->msg, llc, sizeof(union smc_llc_msg));

	/* process responses immediately */
	if (llc->raw.hdr.flags & SMC_LLC_FLAG_RESP) {
		smc_llc_rx_response(link, qentry);
		return;
	}

	/* add requests to event queue */
	spin_lock_irqsave(&lgr->llc_event_q_lock, flags);
	list_add_tail(&qentry->list, &lgr->llc_event_q);
	spin_unlock_irqrestore(&lgr->llc_event_q_lock, flags);
	schedule_work(&link->lgr->llc_event_work);
}

/* copy received msg and add it to the event queue */
static void smc_llc_rx_handler(struct ib_wc *wc, void *buf)
{
	struct smc_link *link = (struct smc_link *)wc->qp->qp_context;
	union smc_llc_msg *llc = buf;

	if (wc->byte_len < sizeof(*llc))
		return; /* short message */
	if (llc->raw.hdr.length != sizeof(*llc))
		return; /* invalid message */

	smc_llc_enqueue(link, llc);
}

/***************************** worker, utils *********************************/

static void smc_llc_testlink_work(struct work_struct *work)
{
	struct smc_link *link = container_of(to_delayed_work(work),
					     struct smc_link, llc_testlink_wrk);
	unsigned long next_interval;
	unsigned long expire_time;
	u8 user_data[16] = { 0 };
	int rc;

	if (link->state != SMC_LNK_ACTIVE)
		return;		/* don't reschedule worker */
	expire_time = link->wr_rx_tstamp + link->llc_testlink_time;
	if (time_is_after_jiffies(expire_time)) {
		next_interval = expire_time - jiffies;
		goto out;
	}
	reinit_completion(&link->llc_testlink_resp);
	smc_llc_send_test_link(link, user_data);
	/* receive TEST LINK response over RoCE fabric */
	rc = wait_for_completion_interruptible_timeout(&link->llc_testlink_resp,
						       SMC_LLC_WAIT_TIME);
	if (link->state != SMC_LNK_ACTIVE)
		return;		/* link state changed */
	if (rc <= 0) {
		smc_lgr_terminate_sched(smc_get_lgr(link));
		return;
	}
	next_interval = link->llc_testlink_time;
out:
	schedule_delayed_work(&link->llc_testlink_wrk, next_interval);
}

void smc_llc_lgr_init(struct smc_link_group *lgr, struct smc_sock *smc)
{
	struct net *net = sock_net(smc->clcsock->sk);

	INIT_WORK(&lgr->llc_event_work, smc_llc_event_work);
	INIT_LIST_HEAD(&lgr->llc_event_q);
	spin_lock_init(&lgr->llc_event_q_lock);
	spin_lock_init(&lgr->llc_flow_lock);
	init_waitqueue_head(&lgr->llc_waiter);
	lgr->llc_testlink_time = net->ipv4.sysctl_tcp_keepalive_time;
}

/* called after lgr was removed from lgr_list */
void smc_llc_lgr_clear(struct smc_link_group *lgr)
{
	smc_llc_event_flush(lgr);
	wake_up_interruptible_all(&lgr->llc_waiter);
	cancel_work_sync(&lgr->llc_event_work);
	if (lgr->delayed_event) {
		kfree(lgr->delayed_event);
		lgr->delayed_event = NULL;
	}
}

int smc_llc_link_init(struct smc_link *link)
{
	init_completion(&link->llc_testlink_resp);
	INIT_DELAYED_WORK(&link->llc_testlink_wrk, smc_llc_testlink_work);
	return 0;
}

void smc_llc_link_active(struct smc_link *link)
{
	link->state = SMC_LNK_ACTIVE;
	if (link->lgr->llc_testlink_time) {
		link->llc_testlink_time = link->lgr->llc_testlink_time * HZ;
		schedule_delayed_work(&link->llc_testlink_wrk,
				      link->llc_testlink_time);
	}
}

void smc_llc_link_deleting(struct smc_link *link)
{
	link->state = SMC_LNK_DELETING;
	smc_wr_wakeup_tx_wait(link);
}

/* called in worker context */
void smc_llc_link_clear(struct smc_link *link)
{
	complete(&link->llc_testlink_resp);
	cancel_delayed_work_sync(&link->llc_testlink_wrk);
	smc_wr_wakeup_reg_wait(link);
	smc_wr_wakeup_tx_wait(link);
}

/* register a new rtoken at the remote peer (for all links) */
int smc_llc_do_confirm_rkey(struct smc_link *send_link,
			    struct smc_buf_desc *rmb_desc)
{
	struct smc_link_group *lgr = send_link->lgr;
	struct smc_llc_qentry *qentry = NULL;
	int rc = 0;

	rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
	if (rc)
		return rc;
	rc = smc_llc_send_confirm_rkey(send_link, rmb_desc);
	if (rc)
		goto out;
	/* receive CONFIRM RKEY response from server over RoCE fabric */
	qentry = smc_llc_wait(lgr, send_link, SMC_LLC_WAIT_TIME,
			      SMC_LLC_CONFIRM_RKEY);
	if (!qentry || (qentry->msg.raw.hdr.flags & SMC_LLC_FLAG_RKEY_NEG))
		rc = -EFAULT;
out:
	if (qentry)
		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
	smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
	return rc;
}

/* unregister an rtoken at the remote peer */
int smc_llc_do_delete_rkey(struct smc_link_group *lgr,
			   struct smc_buf_desc *rmb_desc)
{
	struct smc_llc_qentry *qentry = NULL;
	struct smc_link *send_link;
	int rc = 0;

	send_link = smc_llc_usable_link(lgr);
	if (!send_link)
		return -ENOLINK;

	rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
	if (rc)
		return rc;
	/* protected by llc_flow control */
	rc = smc_llc_send_delete_rkey(send_link, rmb_desc);
	if (rc)
		goto out;
	/* receive DELETE RKEY response from server over RoCE fabric */
	qentry = smc_llc_wait(lgr, send_link, SMC_LLC_WAIT_TIME,
			      SMC_LLC_DELETE_RKEY);
	if (!qentry || (qentry->msg.raw.hdr.flags & SMC_LLC_FLAG_RKEY_NEG))
		rc = -EFAULT;
out:
	if (qentry)
		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
	smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
	return rc;
}

/* evaluate confirm link request or response */
int smc_llc_eval_conf_link(struct smc_llc_qentry *qentry,
			   enum smc_llc_reqresp type)
{
	if (type == SMC_LLC_REQ)	/* SMC server assigns link_id */
		qentry->link->link_id = qentry->msg.confirm_link.link_num;
	if (!(qentry->msg.raw.hdr.flags & SMC_LLC_FLAG_NO_RMBE_EYEC))
		return -ENOTSUPP;
	return 0;
}

/***************************** init, exit, misc ******************************/

static struct smc_wr_rx_handler smc_llc_rx_handlers[] = {
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_CONFIRM_LINK
	},
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_TEST_LINK
	},
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_ADD_LINK
	},
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_DELETE_LINK
	},
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_CONFIRM_RKEY
	},
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_CONFIRM_RKEY_CONT
	},
	{
		.handler	= smc_llc_rx_handler,
		.type		= SMC_LLC_DELETE_RKEY
	},
	{
		.handler	= NULL,
	}
};

int __init smc_llc_init(void)
{
	struct smc_wr_rx_handler *handler;
	int rc = 0;

	for (handler = smc_llc_rx_handlers; handler->handler; handler++) {
		INIT_HLIST_NODE(&handler->list);
		rc = smc_wr_rx_register_handler(handler);
		if (rc)
			break;
	}
	return rc;
}